The function of Protozoa and Bacteria Coexisting in the Mas Culture of the Rotifer Brachionus Plicatilis

本研究旨在了解原生动物和细菌在褶皱臂尾轮虫培养中的作用，作为研究影响海洋动物苗种计划生产的大量死亡或停滞生长的一部分。原生动物和细菌在食物网中的作用按整个养殖周期计算，轮虫的氮素转化率为53.8-70.8%。此外，对于日氮平衡，投喂给动物的氮(1.89×10~(-8)gn/天/轮虫)远远低于生长(1.42)和排泄量(2.69)的总和。这些结果表明，轮虫摄取了作为食物的藻类或酵母以外的有机物质。颗粒计数器检测表明，轮虫排泄物增加的细菌和水生动物都是在形成絮状物后被摄取的，几乎与藻类或酵母菌的摄入量相当。筛选出对轮虫有明显生长促进作用的细菌菌株，该菌株属于假单胞菌。为4-5Log CFU/ml，可能是一种突发性死亡的致病微生物。III.细菌对轮虫养殖中能量和物质流动的作用

This study intended to know the function of both protozoa and bacteria in the culture of the rotifer Brachionus plicatilis, as a part of researches on the massmortality or stagnan growth which disturbs the planned production of marine animal seedlingsI. Function of protozoa and bacteria in food webIncredible value of 53.8-70.8% was obtained in nitrogen conversion rate of the rotifer, when calculated on the whole culture period. Moreover, for daily nitrogen balance, the nitrogen fed to the animal(1.89xlO^<-8>gN/day/rotifer)was far less than the total of growth(1.42)and excretion(2.69). Those results suggested that the rotifer ingested organic substances other than algae or yeasts provided as food. Evaluation with Particle Counter revealed that both bacteria and drotozoa increasing by the use of rotifer's excretion were ingested after forming flocs, which was nearly equal to the value for algae or yeasts.The bacterial strain which showed remarkable growth promotion for the rotifer was isolated, and it belonged to Pseudomonas.II. Function of bacteria as a growth-inhibiting factorThe strain Y5 which had been isolated on the occasion of sudden death of the rotifer had acute virulence to the rotifer, and the 24 hrs' LD_<50> was 4-5 Log CFU/ml, which may be a causative organism of the sudden massmortality.III. Function of bacteria on the energy and substance flow in rotifer culture